JPH0626201B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a method for manufacturing a semiconductor device having a step of ion-implanting using a resist layer as a mask, which is a resist left on a substrate after removing an unnecessary resist layer after ion-implantation. In order to reduce the amount of peeling residue, when removing the resist layer, first, the inorganic contaminants adhering to the resist layer surface during ion implantation are removed by etching, and then plasma is irradiated to decompose the resist layer. It is designed to be removed.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for removing a resist layer used as a mask in an ion implantation process.

In recent years, as semiconductor integrated circuits (ICs) have become higher in density and higher in integration, miniaturization of semiconductor elements and wiring structures as constituent elements has been advanced. As a result, those having a minimum part size of 1 μm or less are practical. It has been converted to. Along with this miniaturization, the amount of adhered substances such as micron-sized dust and contaminants in the manufacturing process has come to influence the manufacturing yield of ICs. It is required to reduce the number of things as much as possible.

In the step of introducing impurities by ion implantation, it is required not only to reduce the contamination during the ion implantation but also to reduce the residue thereof in the step of removing the mask for the subsequent ion implantation.

[Conventional technology]

In the ion implantation method, since it is not necessary to heat the masked substrate to a high temperature unlike other impurity introduction methods such as thermal diffusion method, it is widely used to use an organic resist layer such as photoresist for the mask. It is being appreciated.

After the ion implantation, it is necessary to remove the mask of the resist layer that has become unnecessary, but it is known that the ion-implanted resist layer is less likely to be peeled off because it is partially carbonized. (Kelvin J. Orvek and Craig Huffman;
"CARBONIZED LAYERFORMATION IN ION IMPLANTED PHOTO
RESIST MASKS ”, Nuclear Instruments and Methods in
physics Research B7 / 8 (1985) 501-506.) Since the carbonized resist cannot be removed by the wet method using a resist stripping solution, generally, oxygen (O ₂ The O ₂ plasma ashing method is used to oxidize and remove not only the organic resist but also carbon produced by carbonization of the resist by irradiating plasma.

[Problems to be solved by the invention]

Although it is possible to remove carbonized resist by O ₂ plasma ashing, boron (B) and arsenic (As) ions are ion-implanted at a high concentration of ¹ × 10 ¹⁴ / cm ² or more. In this case, there is a problem that a large amount of resist peeling residue is generated even by O ₂ plasma ashing.

One of the causes for this is that the impurities themselves implanted in the mask are oxidized during O ₂ plasma ashing to form a non-volatile oxide, because the residue is small when argon (Ar) is ion-implanted. Therefore, in order to remove B and As also as volatile hydrogen compounds, a method using a plasma containing hydrogen but not oxygen, such as a nitrogen-hydrogen mixed gas plasma, has been developed.

By this method, even when high-concentration ion implantation of B or As is performed, the resist stripping residue can be reduced to the same level as in the case of Ar ion implantation. However, the size is still 1 μm. There was a problem that the above-mentioned residue remained at about 10 ⁴ per 1 cm ² .

Until now, it was unknown what such residues were. Therefore, after implanting 1 × 10 ¹⁷ / cm ² Ar ions into a silicon (Si) substrate having a resist layer mask and irradiating O ₂ plasma to remove the resist layer, the residue remaining on the Si substrate is removed by Auger electron spectroscopy. (A
When analyzed by the ES method, it was found that the residue contained C, Al and Al ₂ O ₃ , as shown in FIG.

The next issue is which stage of the process where Al and Al ₂ O ₃ that generate residues enter, but when O ₂ plasma ashing is performed only with the resist layer, the number of residues is , 1 cm ² per 10 ^two orders, because it is about 1/100 when the ion implantation, Al, Al ₂ O ₃ is not considered hardly has to be due to the resist.

Now, when oxygen is ion-implanted at about 1 × 10 ¹⁸ / cm ² ,
It has been reported that Al, which is a constituent material of the ion implanter, is sputtered by accelerated ions and Al adheres to the substrate. (S.Nakashima, I.Kawashima and K.Izumi ； “AN A
NALYSYS OF CONTAMINATION IN HIGH-DOSE OXYGEN ION I
MPLANTATION AND A CONTAMINATION-PROOF TECHNIQU
E ”, Proc, 9th Symp.on ISIAT'85 (1985) 203-206.) Therefore, Ar ions were implanted into a silicon substrate at 1 × 10 ¹⁷ / cm ² and AES analysis was performed before and after that, and AES spectra were compared. As shown in Fig. 3 (a), before the ion implantation, only Si, C, and O were detected on the surface of the substrate, but Al was detected on the surface after the ion implantation (the third).
(B)). In addition to Al, P and As were detected,
It is considered that this is because the same device was used for ion implantation of P, As, etc. before this experiment, and the inside of the ion implantation device was contaminated by these.

In addition, when the surface of the resist layer was analyzed by X-ray photoelectron spectroscopy (XPS) before and after the ion implantation of Ar on the silicon substrate with the resist layer attached, in this case as well, the surface of the resist layer before the ion implantation was Although Al was not detected, Al was detected on the surface of the resist layer after the ion implantation as shown in FIGS. 4 (a) and 4 (b). From the bonding state, most of Al is considered to be Al ₂ O ₃ . In addition, in the XPS spectrum, Al
In addition to As, P, S, etc. are also seen. As mentioned above, these are contaminated with As, P, S, etc. in the ion implantation device, and the contaminants attached to the device are Ar. It is considered that the ions were sputtered by ion bombardment during ion implantation and redeposited on the resist layer.

Further, as a result of XPS analysis while sputtering / etching from the surface of the resist layer, it was revealed that Al exists only in a region within about 250 Å from the surface.

AES and XPS analyzes were also performed on those implanted with B ions and As ions, but the same results as in the case of Ar ion implantation were obtained.

Considering the above results together, during the ion implantation, inorganic contaminants such as Al and Al ₂ O _{3 which} are sputtered from the constituent members of the ion implantation device adhere to the surface of the resist layer, and these are O ₂ plasma. It is considered that after irradiation with plasma or hydrogen-containing plasma, it does not become a volatile compound, and thus remains as a residue on the substrate after the plasma treatment.

The present invention has been made in view of the above circumstances, and provides a method for reducing the resist peeling residue in the removal of the resist layer used as a mask for ion implantation, thereby improving the manufacturing yield of semiconductor devices such as ICs. The purpose is to provide.

[Means for solving problems]

The purpose of removing the resist layer used as a mask for ion implantation is to first generate Al generated in the ion implantation apparatus and adhering to the surfaces of the substrate and the resist layer.
This can be achieved by etching away inorganic contaminants including Al ₂ O ₃ and Al ₂ O ₃ and then removing the resist layer by plasma irradiation.

[Action]

As described above, since the main components of the inorganic contaminants that adhere to the surface of the resist layer during ion implantation are Al and Al ₂ O ₃ ,
This can be removed by treating with an alkaline etching solution or the like.

The remaining organic resist layer and its carbide, and impurities such as B and As implanted in the resist layer are decomposed and removed into volatile compounds by irradiation with plasma.

By doing so, the inorganic contaminants do not remain as a residue as in the conventional method, so that the resist peeling residue can be reduced.

There is also a method of using sputter etching to etch the inorganic contaminants adhering to the surface of the resist layer, but this method may damage the surface of the substrate not covered with the resist layer by ion bombardment. There is also a risk that inorganic contaminants adhering to the surface of the substrate will be pushed into the substrate by ion bombardment.
If the inorganic contaminants are dissolved and removed by using an etching solution, the substrate will not be damaged.

〔Example〕

One embodiment of the present invention will be described in detail below with reference to FIG. FIG. 1 is a process chart of one embodiment of the present invention.
In the figure, 1 is a substrate, 2 is a resist layer, 3 is a resist carbonized layer, 4 is an inorganic contaminant, 5 is impurity ions, and 6 is plasma.

Commercially available positive photoresist HPR-204 (manufactured by Fuji Hunt Co., Ltd.) was applied to a thickness of 2 μm on a silicon substrate 1 having a diameter of 4 inches and a surface orientation (100) by a known spin coating method, and then dried nitrogen was used. The resist layer 2 was baked by baking at 140 ° C. for 2 minutes in a gas atmosphere using a hot plate.
Was formed. (FIG. 1 (a)). Next, Ar ions were applied to the surface of the resist layer at an acceleration energy of 70 kev and a dose of 1x.
Ions were implanted under the condition of 10 ¹⁷ / cm ² . By this ion implantation, the resist layer is carbonized to form the resist carbonized layer 3, and at the same time, the inorganic contaminant 4 made of Al, Al ₂ O ₃ or the like is attached. (FIG. 1 (b)). In removing the resist layer 2, first, 38% NH ₄ OH 10 was used.
After cc was immersed in an etching solution diluted with deionized water 1 for 5 minutes, it was bubble washed with deionized water for 10 minutes and dried by blowing dry nitrogen gas. Al and Al ₂ O ₃ are NH ₄ OH
, The inorganic contaminants 4 attached during the ion implantation are removed. In this etching step, it is preferable to apply ultrasonic waves to improve efficiency. Then, using a known barrel type high frequency plasma asher, O ₂ flow rate 200 sccm, pressure 1 Torr, frequency 13.56 MH
O ₂ plasma treatment was performed for 60 minutes under the conditions of z and high frequency input of 300 W (FIG. 1 (d)) to remove the resist carbonized layer 3 and the resist layer 2 (FIG. 1 (e)).

After removing the resist layer, the number of foreign particles having a size of 1 μm or more on the substrate 1 was counted by using a commercially available particle counter (WIS-150; manufactured by Aeronca Electronics Inc.), and the average was 4385 per 1 cm ^2. It was In addition, when the resist layer was removed only by the O ₂ plasma treatment under the same other conditions, the average number of the resist layers was 5788 per 1 cm ² , so that the effect of the present invention is clear. particle·
Since the count value of the counter also includes the number of dust and scratches on the substrate after the O ₂ plasma treatment, the resist stripping residue by the method of the present invention is 3/4 that of the conventional method. It is thought that it became the following. Also,
0.2 as an etching solution instead of diluted ammonia water
Almost the same result was obtained by using an aqueous KOH solution of N.

The concentration of the etching solution and the etching time should be optimized according to the dose of ion implantation, etc.
Needless to say. Further, the etching solution may be any one as long as it can dissolve inorganic contaminants without disposing the substrate,
For example, an etching solution containing phosphoric acid can also be used. Furthermore, sputter etching can be used when damage to the substrate can be ignored. It is also clear from the principle of the present invention that the effect of the present invention does not depend on the type of impurities to be ion-implanted or the type of resist used for the mask.

〔The invention's effect〕

According to the present invention, after the ion implantation using the resist layer as a mask, it is possible to reduce the resist peeling residue remaining on the substrate when removing the unnecessary resist layer, so that the manufacturing yield of semiconductor devices such as ICs can be improved. It has the effect of improving.

[Brief description of drawings]

FIG. 1 is a process diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of AES spectrum of a resist stripping residue, FIG. 3 is a comparison diagram of AES spectra of a substrate surface before and after ion implantation, and FIG. FIG. 4 is a diagram showing an example of an XPS spectrum of a surface of a resist layer after ion implantation. In the figure, 1 is a substrate, 2 is a resist layer, 3 is a resist carbonized layer, 4 is an inorganic contaminant, 5 is an impurity ion, and 6 is a plasma.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 21/306 T 9278-4M

Claims (3)

[Claims] 1. A resist layer 2 formed on one main surface of a substrate 1.
After the ions are implanted into the substrate 1 using the mask as a mask, the ions are generated from inside the ion implantation apparatus during the ion implantation, and the substrate 1
And inorganic contaminants 4 attached to the surface of the resist layer 2
Is removed by using an etching solution, and thereafter, the resist layer 2 is removed by irradiating plasma, and a method of manufacturing a semiconductor device. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the inorganic contaminants 4 are removed by etching with an alkaline etching solution. 3. The etching solution according to claim 2, wherein the etching solution contains at least one of ammonium hydroxide and potassium hydroxide.
A method of manufacturing a semiconductor device according to item.